sqlite doesn't actually support read locks. added a workaround until i can do the...

followup to r108559

diff --git a/includes/ConcurrencyCheck.php b/includes/ConcurrencyCheck.php
index 06f7495..c207eff 100644 (file)
--- a/includes/ConcurrencyCheck.php
+++ b/includes/ConcurrencyCheck.php
@@ -212,7 +212,7 @@ class ConcurrencyCheck {
        }
 
        public function status( $keys ) {
-               global $wgMemc;
+               global $wgMemc, $wgDBtype;
                $dbw = $this->dbw;
                $now = time();
 
@@ -243,8 +243,6 @@ class ConcurrencyCheck {
                        // If it's time to go to the database, go ahead and expire old rows.
                        $this->expire();
                        
-                       // the transaction seems incongruous, I know, but it's to keep the cache update atomic.
-                       $dbw->begin();
                        
                        // Why LOCK IN SHARE MODE, you might ask?  To avoid a race condition: Otherwise, it's possible for
                        // a checkin and/or checkout to occur between this select and the value being stored in cache, which
@@ -258,6 +256,14 @@ class ConcurrencyCheck {
                        //
                        // It appears all the DBMSes we use support LOCK IN SHARE MODE, but if that's not the case, the second
                        // solution above could be implemented instead.
+                       $queryParams = array();
+                       if( $wgDBtype === 'mysql' ) {
+                               $queryParamsp[] = 'LOCK IN SHARE MODE';
+
+                               // the transaction seems incongruous, I know, but it's to keep the cache update atomic.
+                               $dbw->begin();
+                       }
+                       
                        $res = $dbw->select(
                                'concurrencycheck',
                                array( '*' ),
@@ -267,23 +273,29 @@ class ConcurrencyCheck {
                                        'cc_expiration > ' . $dbw->addQuotes( wfTimestamp( TS_MW ) ),
                                ),
                                __METHOD__,
-                               array('LOCK IN SHARE MODE')
+                               $queryParams
                        );
 
                        while( $res && $record = $res->fetchRow() ) {
                                $record['status'] = 'valid';
                                $checkouts[ $record['cc_record'] ] = $record;
 
-                               // safe to store values since this is inside the transaction
-                               $wgMemc->set(
-                                       wfMemcKey( 'concurrencycheck', $this->resourceType, $record['cc_record'] ),
-                                       array( 'userId' => $record['cc_user'], 'expiration' => $record['cc_expiration'] ),
-                                       $record['cc_expiration'] - time()
-                               );
+                               // TODO: implement strategy #2 above, determine which DBMSes need which method.
+                               // for now, disable adding to cache here for databases that don't support read locking
+                               if( $wgDBtype !== 'mysql' ) {
+                                       // safe to store values since this is inside the transaction
+                                       $wgMemc->set(
+                                               wfMemcKey( 'concurrencycheck', $this->resourceType, $record['cc_record'] ),
+                                               array( 'userId' => $record['cc_user'], 'expiration' => $record['cc_expiration'] ),
+                                               $record['cc_expiration'] - time()
+                                       );
+                               }
                        }
 
-                       // end the transaction.
-                       $dbw->rollback();
+                       if( $wgDBtype === 'mysql' ) {
+                               // end the transaction.
+                               $dbw->rollback();
+                       }
                }
 
                // if a key was passed in but has no (unexpired) checkout, include it in the